EVALUATION OF A TETRAHEDRON SPREADER ON A FIXED-WING AIRCRAFT TO INCREASE FERTILISER SPREAD

Abstract

Five combinations of attachments were compared with an unmodified Fletcher aircraft for ability to spread fertiliser granules in a wide swath,over flat land at Napier, North Island. Lateral spread of fertiliser, applied at a nominal rate of approximately 500 kg/ha, was measured by the aircraft flying over a grid of collectors, making two passes for each configuration of attachments. An increase in lateral spread of fertiliser was obtained when theaircraft topdressed in each of the configurations with the tetrahedron spreader fitted but this was accompanied by a marked decrease in rate of application. For example, with the tetrahedron spreader lowered, with streamlining fairings fitted to the front and rear of the hopper outlet, and with accelerator ducts attached to the front f&ring, the swath width increased by 32%. up to 33 m, and the central peak from the distribution pattern, typical of that produced by an unmodified aircraft, was reduced. However the measured application rate fell to approximately 190 kg/ha with this combination of attachments compared with the 427 kg/ha for the unmodified aircraft. Further tests with an unmodrfied aircraft at lower application rates are needed before a direct comparison of swath width can be made. Keywords: Tetrahedron fertiliser spreader, topdressing, lateral spread, fertiliser distribution, hill country